Re: [Buildroot] [PATCH] package/jpeg-turbo: fix aarch64 build using an upstream patch

Hello Alessandro,

On Sun, Jul 26, 2026 at 11:57:26PM +0200, Alessandro Rubini wrote:
> This patch is 3.2.0-8-g0da22762 in the original jpeg-turbo package,
> where the committer claims they can't reproduce the problem. Buildroot
> is currently using version 3.2.0 of the package.
> 
> The build issue I esperience with an aarch64 build (cm4 custom baseboard)
> is the following:
> 
>    spng.c:(.text+0x4d8c): undefined reference to `__fpclassifyf'
> 
> The patch actually fixes it.
> 
> Signed-off-by: Alessandro Rubini <[email protected]>

Thanks for your patch. I was initially not able to reproduce the
issue, but after digging into the autobuilder failures for this
problem, I found out that the key to encounter the problem is
BR2_OPTIMIZE_S=y (i.e use gcc -Os instead of our default of -O2). Do
you confirm you are using BR2_OPTIMIZE_S=y in your configuration?

Overall, I can reproduce the issue with:

BR2_aarch64=y
BR2_TOOLCHAIN_EXTERNAL=y
BR2_TOOLCHAIN_EXTERNAL_BOOTLIN=y
BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_AARCH64_GLIBC_STABLE=y
BR2_OPTIMIZE_S=y
BR2_PACKAGE_JPEG=y

but not with:

BR2_aarch64=y
BR2_TOOLCHAIN_EXTERNAL=y
BR2_TOOLCHAIN_EXTERNAL_BOOTLIN=y
BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_AARCH64_GLIBC_STABLE=y
BR2_PACKAGE_JPEG=y

Do we understand why the issue happens with -Os but not -O2 ?

> diff --git a/package/jpeg-turbo/0001-libspng-Really-remove-gamma-correction-code.patch b/package/jpeg-turbo/0001-libspng-Really-remove-gamma-correction-code.patch
> new file mode 100644
> index 0000000000..5dcd95d0b9
> --- /dev/null
> +++ b/package/jpeg-turbo/0001-libspng-Really-remove-gamma-correction-code.patch
> @@ -0,0 +1,109 @@
> +From 0da22762971551462cfad8f0b11cfb037472a4e8 Mon Sep 17 00:00:00 2001
> +From: DRC <[email protected]>
> +Date: Thu, 16 Jul 2026 12:09:54 -0400
> +Subject: [PATCH] libspng: Really remove gamma correction code
> +
> +We really don't use it, and fpclassify() apparently introduces yet
> +another libm dependency in some cases (although I can't reproduce that.)
> +
> +Fixes #904

We require all patches added in Buildroot to have:

- An "Upstream:" tag that points to the upstream commit, PR or patch
  submission (in your case, commit)

- A "Signed-off-by:" tag from the person who introduced the patch into
  Buildroot, i.e you.

Could you adjust this, together with hopefully some explanation on why
-Os triggers the issue and not -O2?

Thanks a lot!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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